Transversing incore probes (TIPs) are used in the nuclear power industry to calibrate local power range detectors that are located within the housing of a nuclear reactor. The TIP system includes a probe, such as a gamma detector or a neutron detector, fixed on the end of a helix cable. In operation, the helix cable is driven into the reactor core and the probe is moved next to the local power range detector that requires calibration. The helix cable is drawn off a large reel (known as a Gleason reel) on which it is wound. The Gleason reel maintains the helix cable under high tension by means of a spring and acts to draw the helix cable out from the reactor housing. The helix cable is driven through a protective tubing into the reactor housing by a motor connected to a drive chain, which in turn is connected to a gear box connected to a drive shaft that is connected to a drive wheel. The drive wheel (known as a hob wheel) is notched to drivingly engage the helix cable.
Periodically, the torque on the helix cable is measured to ensure that it is not binding within the protective tubing. Such binding can occur for various reasons, including accidental crimping of the protective tubing. A set procedure is used for measuring the torque. First, a C-clamp is placed on the Gleason reel and secured against its housing to prevent the reel from moving and retracting the helix cable. Once the Gleason reel is locked in position, a master link on the drive chain is disconnected and the drive chain is pulled off. Finally, a hand crank and torque wrench are placed on the drive shaft, the C-clamp is removed from the Gleason reel and the torque is measured.
A problem that is encountered during such torque measuring procedure is that during hand cranking, the handle can fall off which enables the Gleason reel to retract the probe. If the probe is withdrawn from the core it may expose personnel to radiation as the probe tip can be very hot depending on where it was located in the core and the amount of time it was located therein.